Church Sound: Solving Mysteries—The Case Of The Missing Audio For Video

The Mystery Deepens
Your typical detective story has the investigator leaving the scene of the crime to return to the station where they start talking about witness, suspects, and potential leads. In my case, I did the same. That is to say, I went home.

Working through my notes the next afternoon, I decided to call a friend and fellow tech who was at the church last night. “Jeff, it’s Chris. Did you hear the messed up video last night?”

“I did,” he replied, “and I was in the sanctuary today and everything in the booth looked good.”

We had a day to go before the regular church service. Things were not looking good.

One important note; while Jeff and I knew how to run sound in our church, looking back, there was a lot we didn’t know.

The next morning, I got a text message from Jeff: “Fixed. Low-pass filter switch was on.” What low-pass filter switch? Better yet, what’s a low-pass filter?

In a follow-up email, Jeff explained that he and a few friends were out late at the church and playing together, musicians that they were, when he starting running audio through the sound system and, well, take it away Jeff:

“I was getting little to no vocals or guitar, but I was getting the bass pieces out of the drum kit clearly. All sound coming through the monitors through the Aviom system was perfect, so that signal path was good…I verified signal lights were blinking appropriately on the mixer, house EQ, Aviom and amp. All checked out. [Finally] I systematically looked at each button and knob. When I got to the [house] LPF switch I didn’t know what it was, everything else looked OK, so I tried flipping the switch, and sound was restored. It wasn’t until later that I consulted the manual to see what LPF stands for. I should have remembered…but at one in the morning the brain wasn’t working too well.”

LPF…on a board-wide master send output…ON AN ANALOG CONSOLE!?!

Lessons Learned
Our analog mixing console, a standard Mackie that many of you have used/still use, has a recessed LPF (low-pass filter) switch. While I understand why it would be recessed, still to this day I can’t imagine why it would have one. I’ve heard a reason or two but I don’t think that they’re good reasons.

There are two key bits of information to take away from this solved mystery.

—Know what every knob, switch, and setting on your console does, whether you use it or not.

—Know that sooner or later, something will get changed and by knowing the settings of your equipment, you’ll know where to look to solve the problem. I’ve seen this on everything from mixing consoles to recording units.

One mystery still remains in this story: we never did discover who flipped on the LPF switch in the first place.